1. Field of the Invention
The present invention relates to a method of measuring the azimuth and resetting to zero azimuth automatically, in particular to a method of precision tuning the longitudinal and latitudinal zero reference values in an azimuth meter in preparation for accurate measurement of the azimuth.
2. Description of Related Arts
Azimuth meters in general are either mechanical or electronic. Mechanical azimuth meters are low cost but their readability and accuracy are not very good. Electronic azimuth meters are favored by mountaineers and navigators as they possess high precision and good readability.
The electronic azimuth meter performs azimuth measuring with two orthogonal magnetic sensors. Intensity values of earth magnetism at the measuring site are collected by the magnetic sensors, and then output the corresponding sine wave signals. The electronic apparatus picks up the sine wave signals representing the earth magnetism at the site, processes the measured values through internal computation, and outputs the azimuth on the screen of the electronic apparatus. Since an electronic azimuth meter can rely on the internal electronic circuits to compute the azimuth, it does not need the realignment of the pointer scaling necessary for mechanical azimuth meters. However, it is necessary to set the conversion standard value, basing on which the sine wave signals output by the magnetic sensors can be processed to compute the azimuth, which means every electronic azimuth meter should have the capability of resetting to zero azimuth automatically in order to generate an accurate measurement of the azimuth.
The current practice of resetting to zero azimuth in an azimuth meter is by using two orthogonal oriented magnetic sensors to take sample measurements orthogonally. Since the two sine wave signals output by the two magnetic sensors are each out of phase by 90 degrees, the computation for the azimuth can be simplified by taking the two values having 90 degrees phase angle as the zero reference values. The output sine wave signals represent the magnitude of earth magnetism at the measuring site in the longitudinal and latitudinal orientations. If the measuring site is located in both high longitudinal and latitudinal coordinates, the amplitude of the sine wave signals will tend to increase in proportion to the angular coordinate, but if the measuring site is located in positions with large difference between the longitudinal and latitudinal coordinates, then the amplitude of the sine wave signals will vary greatly. Even with adjustment of zero azimuth at the first measuring site (x1, y1) to generate adjusted zero reference values (X0, Y0). If the measuring site is moved to a second location (x2,y2), the computation of the azimuth still causes overflow errors. Therefore, the precision and applicability of conventional azimuth meters, as shown in FIG. 5, are considerably discounted.